Photographic developer containing thallium salts



Patented Oct. 30, 1951 PHOTOGRAPHIC DEVELOPER CONTAINING THALLIUM SALTS James E. Bates, Binghamton, N. Y., assignor to General Aniline & Film Corporation, New York, N. Y., a corporation of Delaware No Drawing. Application October 30, 1947, Serial No. 783,224

3 Claims.

' This invention relates to the development of photographic emulsions of the reversible color type on films and other transparent materials for the production of positive color transparencies and the development of such emulsions on paper and other printing material'for the production of color positive prints from the said transparencies by the color reversal process and, in particular, it relates to improvements in the developing solutions and in the process of developing the color reversal emulsions.

This application is a continuation-in-part' of my application Serial No. 541,649 filed June 22, 1944, for Photographic Emulsion Development (now abandoned).

In the commercial practice of developing photographic emulsions where a large quantity of the photographic film is to be developed, it is desirable that all the film be subjected to the developing solution for the same length of time. However, this is rendered difiicult because after a number of photographic films have been developed in a given solution, there is a gradual change in tone of the developed film and a loss of developing energy of the solution. Consequently, unless the time of development is increased, it is not possible to produce a satisfactory density and contrast. Heretofore it was believed that loss in developing energy of the solution, and consequent increase in time of development, was due to depletion of the developing agent and it has been proposed to maintain a relatively uniform development time by replenishing the developer solution. Such replenishment has not been satisfactory as there occurs a relatively large shift in development energy of the solution for each portion of film developed for which adequate compensation can be made only by increasing the time of development.

The contrast obtained with a given exposure of film is dependent to a large extent upon the time of development, but a maximum contrast is limited by the maximum gradation of the curve representing density plotted against the logarithm of the time of development. For many purposes a high contrast is desirable, as in the case of multilayer color film to be developed by the reversal process. In the development of this type of film, it is highly desirable to obtain a high contrast while at the same time maintaining the time of development as small as possible. It is, therefore, an object of this invention to improve the developing solutions employed in the development of photographic reversible type multicolor emulsions on films, plates, papers and the like.

The developing process for multicolor reversible emulsions consists of six essential steps with washes and rinses interposed where necessary. After exposure of such an emulsion, it is developed in a metal-hydroquinone developer. This develops to metallic silver the three tri-color separation images recorded in the emulsion layers of a tri-pack multilayer color material. No color is formed during this development, which is designated as the first development, since color can 'only be formed when the film is developed in the proper color forming developer. After this first development, the film is rinsed, then shortstopped in an acetic acid short-stop to arrest development. After short-stopping, the film is washed and re-exposed. During this re-exposure or second exposure, all silver halides in the film which were not previously exposed in the camera and which did not develop in the first developer now become exposed and are ready for develop ment in the color forming developer. These silver h'alides make up the positive image. In the color forming developer, these silver halides are reduced to metallic silver by the reaction of the developer. Simultaneously with the reduction of the silver halides to metallic silver, reaction products which generally occur in developing are produced. In a normal black and white film these reaction products difiuse through the gelatin and are finally washed out in the developer and subsequent baths. However, in the color film these reaction products combine with the color formers originally placed in the film and produce dye in proportion to the amount of silver halides which were reduced. Thus, as the three positive images in the film develop to metallic silver three separate dye images are formed in situ with the silver images. No color is formed around the negative image because this image is already in the reduced or metallic silver state as a consequence of the first development and no further reduction A can take place.

It has been determined that the addition of soluble thallium salts, such as thallous and thallic nitrate, thallous and thallic sulfate, and thallous hydroxide, to the first developer for a re- .versal multilayer color film or paper emulsion materially improves the developing characteristics and prolongs the life of the developer. When unusually high emulsion speeds and increased contrasts are obtained, for example,

when 50 mg. of thallium nitrate are added to a first developer of the metol-hydroquinone type and the resulting developer is used to develop a reversible color printing material exposed in a camera using a Weston speed rating of 12, ad-

,1 equately exposed pictures will be obtained when first developed only 8 minutes. In the absence of the thallium compound, the same developer requires three times as much exposure and a first development time of minutes to secure a comparable picture. When the thallium compound is omitted from the developer, it is necessary to extend the development time to minutes order to secure an emulsion speed of 12 which is secured b only 3 minutes development with'the thallium compound present. When the first development is thus extended in order to secure this additional speed, the color bale rice, is altered radically because of the uneven degree of; level: opment of the various layers of the color film. When a thallium compound is used, the-layers develop evenly and no disturbing unbalance results. The use of thallium compounds in the first development, ther efore, permits higher emulsion speed and at the same time allows maintenance of better color balance and better eontrast than could be O tained by any length ofdevelopin g time without the thallium com; pound in the developer.

" th i n e'tlial o p und n. he first developer tor reversal color film or printing a a m si ns s h ha it w l f t ha fi t q f hfil fitg dev e tions. In applying the invention to the revivifying oi ,developer solutions, a soluble thallium salt is 'ntermittently added in small increments define t e bem nt pre sh e ui ed am u the. s9l b e tha l um l y be introdueed intermittently after a predetermined quantity of the film has passed through the de veloping solution or, where the'film is developed continuously, the soluble thallium salt may be added continuously'until the developer is substantially exhausted desired, the developer and other ingredients of the developing solution also be replenished by addition of suitable uant t s Q? d el per re a nd alka along with suitable quantities of the soluble, thallium salt to maintain the desired proportions I this method o replenis i de elo er 11:- tions, a relatively small quantity of the. soluble, halli m Salt is? teed pr i rre a o b in about 0.001 to 0.005 gram per square foot of; m iqn de elo ed dep n in po he de ree 01 e haus i n i; he d v l pe Th salt s. added to the solution after partial exhaustion.

In order to, obtain the maximum effect. on contrasts, rate of development and emulsion. speed, the. soluble thallium salt is added to the fresh. developer solution before commencing to develop emulsions therein, aquantity in the order of about 0.01110 0.1 gram per liter of developer solution being employed. A metol-hydroquinone develope'rof the type used for the first development of a reversal multicolor film emulsion which has been so treated will develop more film that asimilar developer which has not been treated by the addition of, such quantities of soluble thallium salts, and when used as the V first developer for'a reversal color film emulsion or a reversal color printing paper emulsion; will develop such emulsions in approximately half the time and produce higher contrasts than in the case of a developer which. has not been treated with the thallium compound.

The following examples will serve to further illustrate this invention and the best manner of carrying it out, it being understood that the materials and proportions therein recited are given by way of illustration and not intended 4 as limitations. Unless otherwise specified, the parts are by weight.

Example I Multilayer color film of the type containing color formers in situ in the color sensitive layers, such as that which is currently on the market and known as Ansco Color Film (reg. it. is ormally processed by the following procedure Eirst developed; 12 at 68 F. in the following solution:

Grams -'7'.T -'T-"Z"'."": 3 Sodium sulfite 50 Hy dro'quinone 6 Sodium carbonate 40 Sodium thiocyanate f 2 ti assium brom de -fl- 2 Wat d ma e 11- 2. Rinsed If in running water.

3. Hardened 5 ma 3% solution of potassium chrome alum. 4. znd 'exposed to light of photofiood lamp for 3'. I 5. Color developed 18' in the followin 5. 1- tion:

Water to make 1 1;.

7.. Hardened 5'- in a potassiu m chrome alum solution.

' 8. Washeclfi'.

9. Bleached 1 0 in Potassium, ferricyanide Water to, make, 1; l.

Sheet processed e. firs deve o er. T as;

thus partially exhausted firstfdeveloper solution: was added @010 g. thallous nitrate and an addi tionalsheet was given first development andthe subsequent steps to complete the reversal'processi' Thesheet processed after-the thallousnitr-ate addition to thefirst developershowed that-the speed of'the film had been restored towithin;20 of the original, speed. Furthermore, the colon of the f lm developed in this solution, was not impaired.

Example I I O ell 0f he first developer prepared asde; scribed in Example I was used for developing' 25-8 x exposed multilayer color film batches of 5 sheets'at a time. The developer exhausted progressively and produced progressively lower emulsion speeds in the film and when all had been developed, the film showed only about onequarter the original emulsion speed. In a similar solution the same quantity of'film was processed in the same stages but -the developer solution was replenished by the addition of 80 cc. of the following replenished solutionafter each development of 5 sheets of film:

. 1 I Grams Metol 4 Sodium sulfite 50 Hydroquinone 8 Sodium carbonate 40 Sodium thiocyanate 5 Water, 1 1.

With replenishment in this manner the emul- Example III Multilayer color film of the reversal type was processed according to the procedure in Example I except that the first developer solution contained 0.100 gram of thallium hydroxide per liter. This film showed an emulsion speed of about 24 Weston and a gamma of about 3 to 4. Development of a similar film in a similar first developer solution having no added thallous hydroxide showed an emulsion speed of about 8 Weston and a gamma of about 1 to 2.

Example IV It is often desirable to obtain a color print directly from a camera exposure instead of first making a color transparency original and then making a print from the original ,on another multilayer reversible color print material such as Ansco Color Printon (reg. T. M.). The pictures can be made directly on the Ansco Color Printon, but the use of this as a camera material is limited because of the low emulsion speed. Attempts have been made to increase the emulsion speed to the usable level by employing greatly extended first development times. By using a development time of 20 to 24 minutes at 68 F., barely passable emulsion speeds to the order of 1 to 2 Weston have been obtained. Further increases of development time beyond 24 minutes give washed out prints and unbalanced colors. Such a procedure would be carried out as follows:

1. First develop 24' at 68 F. in the following solution:

Water to make 1 l.

2. Short stopped 3' after the first developer in Sodium bisulfite; 50 g. Water to make 1 l.

3. Wash for 2'.

4. Second exposed 2.

5. Color developer 12' in the following developer: i v

1 Grams P-amino diethyl aniline HCl 4 Sodium sulfite 20 Sodium carbonate Hydroxylamine HCl '1 Potassium bromide 2.5

6. Rinse 1'.

7. Harden 5 in a solution of 3% potassium chrome alum.

8. Wash for 10'.

9. Bleach 10 in the following solution Water to make 1 1.

12. Wash 10'. 13. Dry.

A camera exposure made directly on Ansco Color Printon using an exposure second at M5 and processed as above gave satisfactory color prints.

However, it was determined that if .05 gram per liter of thalloussulfate were added to the first developer the required first developing time could be reduced to 12 minutes at 68 F. and would give a satisfactory development as compared to 24 minutes without the thallous salt. Furthermore, the emulsion speed thus obtained with the thallous salt is three times as much as that of the plain developer, the gradation is made more brilliant and pleasing, and the color balance is not disturbed as much as by increased development time with the plain developer.

I claim:

1. A photographic developer solution for the initial development of an exposed color reversal photographic element having at least one silver halide emulsion layer containing color formers which will couple with the oxidation product of a p-phenylene diamine developing agent to form the dye image whichcomprises metol, hydroquinone, and. a soluble thallium salt, the latter being in the proportion of 0.01 to 0.1 gram of the thallium salt per liter of solution, said developer solution being incapable of reacting with the color formers.

2. The photographic developer solution of claim 1 wherein the soluble thallium salt is thallium nitrate.

3. A photographic developer solution for the initial development of a reversal color photographic element having at least one silver halide emulsion layer containing color formers which will couple with the oxidation product of a pphenylene diamine developing agent to form the dye image which comprises metol, hydroquinone,

sodium sulfate, sodium carbonate, sodium thiocyanate, and from 0.0 1 to 0.1 gram of thallium nitrate per literof solution, said developer solution being incapable of reacting with the color formers.

JAMES E. BATES.

' REFERENCES CITED UNITED STATES PATENTS Name Date Kieser Sept, 8, 1936 Number Number Name Date 2,013,621 Blaney Man. 16, 193.7 2,105,27 Steigmann Jan. 11, I938 FOREIGN PATENTS 5 ll i lbera CQun Date 1 52 Gre r tain Jan- 4, 1. 3

OTHER REFERENCES- Ha dr hg Photo r phisq e K t spond nz, 10 Band 73, 1937. pp. 129-134, all cited,

Haidrich, Photographische Korrespondenz,

Bandl'li, 193 8, pp. 8-13, all cited. 

1. A PHOTOGRAPHIC DEVELOPER SOLUTION FOR THE INITIAL DEVELOPMENT OF AN EXPOSED COLOR REVERSAL PHOTOGRAPHIC ELEMENT HAVING AT LEAST ONE SILVER HALIDE EMULSION LAYER CONTAINING COLOR FROMERS WHICH WILL COUPLE WITH THE OXIDATION PRODUCT OF A P-PHENYLENE DIAMINE DEVELOPING AGENT TO FORM THE DYE IMAGE WHICH COMPRISES METOL, HYDROQUINONE, AND A SOLUBLE THALLIUM SALT, THE LATTER BEING IN THE PROPORTION OF 0.01 TO 0.1 GRAM OF THE THALLIUM SALT PER LITER OF SOLUTION, SAID DEVELOPER SOLUTION BEING INCAPABLE OF REACTING WITH THE COLOR FORMERS. 